Acoustic wave measuring apparatus and control method of acoustic wave measuring apparatus

ABSTRACT

Provided is an acoustic wave measuring apparatus including: an acoustic probe; region-of-interest setting unit for setting two or more regions of interest for an object; priority setting unit for setting priorities on the regions of interest; region calculating unit for determining, for each of the set priorities, an inclusion region including the regions of interest set with the priority; scanning method determining unit for assigning a scanning stripe to each of the inclusion regions so as to include all regions of interest included in the inclusion region; scanning path identifying unit for determining a scanning order of a plurality of scanning stripes having a same priority so as to shorten a movement distance of the acoustic probe; and scanning unit for scanning the scanning stripes according to the determined scanning order, based on the priority order, by moving the acoustic probe.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/649,672,filed Oct. 11, 2012, claims benefit of that application under 35 U.S.C.§ 120, and claims benefit under 35 U.S.C. § 119 of Japanese PatentApplication No. 2011-242271, filed on Nov. 4, 2011. The entire contentsof each of the mentioned prior applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an acoustic wave measuring apparatusand a control method of such an acoustic wave measuring apparatus.

Description of the Related Art

An ultrasound measuring apparatus of imaging the structure inside abiological object by transmitting ultrasound waves to the biologicalobject and analyzing the reflected ultrasound waves has been put intopractical application in the medical area. When ultrasound waves aretransmitted to the biological object, the reflection of ultrasound wavesoccurs at the interfaces in the biological object having differentacoustic impedances. An ultrasound measuring apparatus imagesconfiguration information in the biological object by analyzing thereflected waves and detecting the interfaces.

Moreover, in recent years, technology has been devised for analyzing thestructure and condition of the surface and inside of a biological objectby irradiating a laser beam onto the biological object and generatingacoustic waves (photoacoustic waves) caused by such laser irradiationfrom the inside of the biological object, and analyzing suchphotoacoustic waves (U.S. Pat. No. 5,840,023). This technology is alsoreferred to as photoacoustic wave measurement, and there isconsideration for diverting this technology to medical use, such as forthe examination of the inside of the human body, since examination canbe performed non-invasively.

Both of the apparatuses described above use an acoustic probe forreceiving the ultrasound waves. As the acoustic probe, there are typeswhich are handheld and used by being manually pressed against the skinnear the region of interest which the user wishes to acquireinformation, and types which mechanically scan the surface of the skinof the biological object by introducing a mechanical scanning mechanism.

With existing acoustic probes, it is difficult to produce a sensor witha large opening as with an X-ray imaging apparatus from the perspectiveof production yield and cost. Thus, the generally adopted method is touse an acoustic probe of a size that is smaller than the region thatneeds to be examined and covering such region to be examined viaautomatic or manual scanning.

A measuring apparatus which mechanically drives an acoustic probeincludes an input setting unit to be used by the user for setting theregion of interest. The input setting unit is configured, for example,from devices such as a keyboard, a mouse, or a touch pen, and is usedfor setting the region of interest by inputting the detailed measurementsetting, or designating the measuring position. Among the foregoingapparatuses, there are types which enable the user to designate, indetail, the scanning track of the probe by using a touch pen or the like(Japanese Patent Application Laid-Open No. 2006-000185). A measuringapparatus performs measurement while moving the acoustic probe so as totrace the designated scanning track.

-   Patent Literature 1: U.S. Pat. No. 5,840,023-   Patent Literature 2: Japanese Patent Application Laid-Open No.    2006-000185

SUMMARY OF THE INVENTION

A conventional measuring apparatus has a problem in that much time isrequired for measuring an object in both photoacoustic measurement andultrasound measurement. For example, with mammography for examiningbreast cancer, the suspected site is compressed and fixed formeasurement, and the time that imposes burden on the subject due tocompression is preferably short.

In fact, the level of burden felt in response to the compression andfixation will vary among different individuals, and certain subjects areunable to withstand such compression and fixation for a long period oftime. Generally speaking, in measurement using ultrasound waves andphotoacoustic waves, higher examination accuracy can be obtained as thethickness of the suspected site is shallower. Thus, in order to ensurethe required examination accuracy, a certain level of compressiveholding is required.

Due to the foregoing circumstances, the measurement time is desirably asshort as possible. Nevertheless, when there are a plurality of setregions of interest, the acoustic probe makes a round by scanning allregions and, therefore, the movement distance increases, and there is aproblem in that wasted time results depending on the scanning order.

Moreover, even in cases where the measurement is suspended midway, dataof a location of high measurement priority is preferably acquired asmuch as possible. When a plurality of regions of interest aredesignated, it is possible to deal with the foregoing case by assigninga priority to each of the plurality of regions of interest andperforming scanning in that priority order. Nevertheless, for aconventional apparatus to deal with the foregoing problem, the user wasrequired to personally be aware of the foregoing circumstances anddesignate the scanning track in order from the location of highestpriority, and the operation was complicated.

The present invention was devised in view of the foregoing problems, andan object of this invention is to provide an acoustic wave measuringapparatus capable of simplifying the setting operation to be performedby the user, and determining a scanning path among a plurality ofregions of interest according to a priority order.

In order to achieve the foregoing object, the present invention providesan acoustic wave measuring apparatus, comprising:

an acoustic probe;

a region-of-interest setting unit configured to set two or more regionsof interest for an object;

a priority setting unit configured to set priorities on the regions ofinterest that have been set;

a region calculating unit configured to determine, for each of the setpriorities, an inclusion region including the regions of interest setwith the priority;

a scanning method determining unit configured to assign a scanningstripe, which is a rectangle that is formed by moving the acoustic probein a scanning direction, to each of the inclusion regions so as toinclude all regions of interest included in the inclusion region;

a scanning path identifying unit configured to determine a scanningorder of a plurality of scanning stripes having a same priority so as toshorten a movement distance of the acoustic probe; and

a scanning unit configured to scan the scanning stripes according to thedetermined scanning order, based on the priority order, by moving theacoustic probe.

The present invention also provides a method of controlling an acousticwave measuring apparatus having an acoustic probe, comprising the stepsof:

receiving a designation of two or more regions of interest for anobject;

receiving a designation of priorities on the regions of interest thathave been set;

determining, for each of the designated priorities, an inclusion regionincluding the regions of interest;

assigning a scanning stripe, which is a rectangle that is formed bymoving the acoustic probe in a scanning direction, to each of theinclusion regions so as to include all regions of interest included inthe inclusion region; and

determining a scanning order of a plurality of scanning stripes having asame priority so as to shorten a movement distance of the acousticprobe,

wherein the scanning stripes are scanned according to the determinedscanning order, based on the priority order, by moving the acousticprobe.

According to the present invention, it is possible to provide anacoustic wave measuring apparatus capable of simplifying the settingoperation to be performed by the user, and determining a scanning pathamong a plurality of regions of interest according to a priority order.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system configuration diagram of the photoacoustic measuringapparatus according to an embodiment of the present invention;

FIG. 2 is a setting screen example of the region of interest by theregion designating unit;

FIG. 3 is a processing flowchart of the controller unit according to thefirst embodiment;

FIG. 4 is a schematic diagram in the case of setting a plurality ofregions of interest;

FIG. 5 is a schematic diagram of the inclusion region relative to theregion of interest according to the first embodiment;

FIG. 6 is an example of the stripe assignment to the inclusion regionaccording to the first embodiment;

FIG. 7 is a schematic diagram of determining the scanning region in thenotable stripe according to the first embodiment;

FIG. 8 is a detailed explanatory diagram of the processing flowchart ofthe controller unit;

FIG. 9 is a schematic diagram of data accumulation based on thecontinuous scanning by the acoustic probe;

FIGS. 10A and 10B are schematic diagrams of the overlapping region ofthe regions of interest and cumulative data according to the secondembodiment; and

FIG. 11A to 11D are schematic diagrams in a case where an excess datameasurement region occurs according to the third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention are now explained in further detailwith reference to the drawings. Note that, as a general rule, the samereference number is given to the same constituent elements and theexplanation thereof is omitted.

(System Configuration)

Foremost, the configuration of an acoustic wave measuring apparatus towhich the present invention can be applied is explained taking aphotoacoustic measuring apparatus as an example with reference to FIG.1, which is a system configuration diagram. The photoacoustic measuringapparatus according to an embodiment of the present invention is aphotoacoustic imaging apparatus for acquiring information (in particularimaging) inside the object. The photoacoustic measuring apparatusenables the imaging of information of a biological object as the objectfor the diagnosis of malignant tumors and vascular diseases or thefollow-up of chemical treatment. Information of a biological objectrefers to the generation source distribution of the acoustic waves thatwere generated based on the irradiation of light, and shows the initialsound pressure distribution in the biological object or the light energyabsorption density distribution derived therefrom.

The photoacoustic measuring apparatus according to an embodiment of thepresent invention is configured, in a broad sense, from a measuringapparatus 100 and an operating apparatus 200. The measuring apparatus100 is an apparatus for performing measurement using photoacousticwaves, and the operating apparatus 200 is an apparatus for operating themeasuring apparatus 100. The measuring apparatus 100 includes a laserlight source 101, an optical system 102 and a light source drive unit106, compression plates 103 a and 103 b, an acoustic probe 104 and aprobe drive unit 105, an apparatus control unit 107, a camera 108, and asignal processing unit 109. Moreover, the operating apparatus 200includes a region designating unit 201, an image generating unit 202, animage display unit 203, and a system control unit 204. The objectmeasuring method is now explained while explaining the configuration ofthe respective components.

An object (not shown) such as a biological object is fixed bycompression plates 103 a, 103 b for compressing and fixing the suspectedsite from either side thereof. Note that, when it is not necessary todifferentiate the compression plates 103 a and 103 b, a collectivedesignation of “compression plate 103” will be used. The laser lightsource 101 is means for generating a laser beam to be irradiated ontothe object, and can be moved planarly in a two-dimensional direction bythe light source drive unit 106, which is drive means. The laser beamgenerated by the laser light source 101 is guided to the surface of thecompression plate 103 a by the optical system 102 such as a lens, amirror, or an optical fibre, becomes dispersed pulsed light, andirradiated on the object.

When a part of the energy of light that propagated inside the object isabsorbed by a light absorber such as blood vessels, acoustic waves aregenerated based on thermal expansion from that light absorber. Acousticwaves are typically ultrasound waves, and include those which arereferred to as sound waves, ultrasound waves, acoustic waves,photoacoustic waves, and light-induced ultrasound waves. In other words,the temperature of the light absorber increases pursuant to theabsorption of the pulsed light, volume expansion occurs due to suchtemperature rise, whereby acoustic waves are generated.

This phenomenon is generally referred to as the photoacoustic effect,and it is possible to acquire the generation source distribution ofacoustic waves that were generated based on the irradiation of light,initial sound pressure distribution in the object, or light energyabsorption density distribution or absorption coefficient distributionderived from the initial sound pressure distribution, and concentrationdistribution of the substance configuring the tissues. The concentrationdistribution of a substance is, for example, oxygen saturationdistribution and oxygenated and deoxygenated hemoglobin concentrationdistribution.

The acoustic probe 104 for detecting acoustic waves corresponds to adetector configured from a plurality of receiving elements which detectthe acoustic waves that were generated in or reflected from the object.A detector detects acoustic waves that were generated in the object, andconverts the acoustic waves into an electric signal, which is an analogsignal. The detection signal acquired by the detector is referred to asa photoacoustic signal. The acoustic probe 104 can also move planarly ina two-dimensional direction by the probe drive unit 105, which is adrive mechanism.

Note that, while an embodiment of the present invention acquiresinformation of an object by using photoacoustic waves, it is alsopossible to acquire object information by internally providing anultrasound source in the acoustic probe 104 for transmitting ultrasoundwaves to the object, and receiving the ultrasound waves that werereflected inside the object. In the foregoing case, the acquired objectinformation refers to information which reflects the difference in theacoustic impedances of the tissues inside the object.

The signal processing unit 109 is means for acquiring internalinformation of the object from the photoacoustic signal. Thephotoacoustic signal acquired from the acoustic probe 104 is amplifiedby a reception amplifier, and converted into a digital signal by an A/Dconverter. The digital signal is communicated to the operating apparatus200 via a communication line, operated into three-dimensionalinformation based on image reconfiguration processing, and thereafterdisplayed as image information on the image display unit 203.

With an embodiment of the present invention, in addition to the above,provided are region of interest designating means (not shown) for theuser to designate the region of interest, a camera 108 for providing anobserved image of the object to be referred to upon designating theregion of interest for the object, and an apparatus control unit 107 forcontrolling the operation of the measuring apparatus 100. The laserlight source 101, the optical system 102, the compression plate 103, theacoustic probe 104, the camera 108, and the region designating unit 201are now explained in further detail.

<Laser Light Source 101>

When the object is a biological object, irradiated from the light sourceis light of a specific wavelength that is absorbed by a specificcomponent among the components configuring the biological object. As thelight source, preferably used is a pulsed light source capable ofgenerating pulsed light of several nanoseconds to several hundrednanoseconds, and at least one pulse sound source capable of generatingpulsed light of 5 nanoseconds to 50 nanoseconds is provided. While laseris preferable as the light source, a light-emitting diode or the likemay also be used in substitute for a laser. As the laser, solid-statelaser, gas laser, dye laser, semiconductor laser and other lasers may beused.

Moreover, light may also be irradiated from the acoustic probe side, orirradiated from the side that is opposite to the acoustic probe. Inaddition, light may also be irradiated from either side of the object.Moreover, in this embodiment, while a single light source is shown as anexample, a plurality of light sources may also be used. In the case ofusing a plurality of light sources, a plurality of light sources thatoscillate the same wavelength may be used in order to increase theirradiation intensity of the light to be irradiated on the biologicalobject, or a plurality of light sources having a different oscillationwavelength may be used in order to measure the difference in thewavelength of optical characteristic value distribution. Note that, asthe light source, if it is possible to use dyes or OPO (OpticalParametric Oscillators) capable of converting the oscillationwavelength, it is also possible to measure the difference in thewavelength of optical characteristic value distribution.

Light shows electromagnetic waves including visible light and infraredlight, and specifically light of a region between 500 nm and 1300 nm,preferably light of a region of 700 nm to 1100 nm with low absorption inthe biological object, is used. However, when obtaining the opticalcharacteristic value distribution of the biological object tissue whichis relatively near the biological object surface, a wavelength regionthat is broader than the foregoing wavelength region; for instance, awavelength region of 400 nm to 1600 nm may also be used. Of the lightwithin the foregoing range, a specific wavelength may be selected basedon the components to be measured.

Moreover, with a laser light source, the irradiation frequency isusually determined in advance. The irradiation frequency is preferablyhigh as possible since the irradiation frequency affects the number ofphotoacoustic measurements that can be performed per unit time. In thisembodiment, the irradiation frequency of the laser light source is 10Hz.

<Optical System 102>

The optical system 102 is, for example, a mirror which reflects light, alens which focuses, expands or changes the shape of light, a prism whichdisperses, refracts and reflects light, an optical fibre whichpropagates light, a diffuser panel, or the like. Light that isirradiated from the light source can be guided to an object by using anoptical member such as a lens or a mirror, or propagated by using anoptical member such as an optical fibre. The foregoing optical membersmay be of any type so as long as the light emitted from the light sourcecan be irradiated, in the intended shape, onto the object.

Note that, generally speaking, rather than focusing the light with alens, it is more preferable to broaden the area to a certain extent fromthe perspective that the diagnosis region can be expanded. Moreover, theregion where light is irradiated onto the object (hereinafter referredto as the “irradiation region”) is preferably movable. By causing theirradiation region to be movable, light can be irradiated to a broaderrange. Moreover, preferably, the irradiation region can be moved insynch with the acoustic probe 104. As the method of moving theirradiation region, a method of using a movable mirror or a method ofmechanically moving the light source itself may be adopted.

<Compression Plate 103>

The compression plate 103 retains at least a part of the shape of theobject to be constant, and is provided between the object and theacoustic probe 104. When the object is sandwiched from either side usingthe compression plates, the position during measurement is fixed, and itis thereby possible to reduce the positional errors caused by bodymotion or the like. Moreover, by compressing the object, light canefficiently reach the deep part of the object. As the holding member,preferably used is a member having high optical transmittance and highacoustic compatibility with the object and the acoustic probe. In orderto improve the acoustic compatibility, an acoustic matching member suchas a gel may be interposed between the compression plate and the object,and between the compression plate and the acoustic probe.

<Acoustic Probe 104>

The acoustic probe 104 is a device which detects acoustic waves andconverts the detected acoustic waves into an electric signal. Thephotoacoustic waves generated from a biological object are ultrasoundwaves of 100 kHz to 100 MHz. Thus, as the acoustic probe 104, anultrasound detector capable of receiving the foregoing frequency band isused. Note that any detector may be used so as long as it is able todetect the acoustic wave signal and convert the acoustic wave signalinto an electric signal; for instance, a transducer that uses thepiezoelectric phenomenon, a transducer that uses the oscillation oflight, or a transducer that uses the change in capacity. Note that adetector is preferably configured by a plurality of receiving elementsbeing arrayed two-dimensionally.

As a result of using such two-dimensional arrayed elements, acousticwaves can be simultaneously detected at a plurality of locations, and itis possible to shorten the detection time as well as reduce theinfluence of vibration of the object and so on. In an embodiment of thepresent invention, let it be assumed that the receiving element pitch isa 2 mm interval, the receiving element array is five elements in themain scanning direction (direction in which the acoustic probe moveswhile performing the scan), and five elements in the sub scanningdirection (direction that is orthogonal to the main scanning direction).

<Camera 108>

The photoacoustic measuring apparatus according to an embodiment of thepresent invention includes a camera 108 for providing images to bereferred to by the user upon designing the regions of interest to besubject to photoacoustic measurement. The camera 108 is installed in adirection that is orthogonal to the holding plates that compress andhold the object, and the captured image is transmitted to the operatingapparatus 200, and displayed as the observed image. The visual field ofthe camera is preferably installed at a view angle in which thephotoacoustic measurable range can be viewed. The camera is installed sothat the compressed and held object can be observed, and the user candesignate the region of interest while observing the compressed and heldobject.

<Region Designating Unit 201>

The photoacoustic apparatus according to an embodiment of the presentinvention includes a region designating unit 201 as means for the userto designate the region of interest to be imaged. The user designatesthe region for imaging the region of interest by using input means suchas a mouse while referring to the observed image of the compressed andheld object that is displayed on the display device. The input means isnot limited to a mouse or a keyboard, and may also be a tablet type or atouch pad mounted on the display device surface. In this embodiment, aplurality of regions of interest can be designated.

In an embodiment of the present invention, in order to associate theobserved image and the scanning surface of the acoustic probe, thecamera 108 is installed so as to capture the observed image of a surfacethat is parallel to the plane to be scanned by the acoustic proberelative to the object. The user can designate the region to be scannedwith the probe by setting a two-dimensional rectangle (measurementdesignated region) at a location corresponding to the position to bemeasured while referring to the observed image captured by the camera.Note that the measurement designated region may also be a shape otherthan a rectangle.

As the method of designating the measurement region, coordinates mayalso be designated based on input using a keyboard. The coordinatedesignating method in the foregoing case may be the designation ofcentral coordinates of the measurement region of a predetermined size inorder to specify the measurement region, or a plurality of vertexcoordinates may be designated on the reference image plane so as to setthe measurement designated region. In all of the foregoing cases, it ispossible to set a measurement designated region as the two-dimensionalrectangular region on the reference image plane.

The photoacoustic measuring apparatus according to an embodiment of thepresent invention converts the image coordinate system of the camerainto an apparatus coordinate system based on the designated measurementdesignated region, and performs control so as to move the probe to acorresponding position of the actual object.

The screen image for designating the region in this embodiment is shownin FIG. 2. In the diagram, 301 represents an observed image from aspecific direction relative to the object, and 302 represents ameasurement designated region that was designated by the user whilereferring to the observed image. With respect to the measurementdesignated region 302, it is possible to designate a region of anarbitrary size through operations such as disposing a rectangle of apre-set size, or inputting a rectangle using a pointing device.

Moreover, a function for designating a plurality of measurementdesignated regions is also provided. For example, this is a method wherea multiple selection button is provided and, when the measurementdesignated region is designated while pressing the multiple selectionbutton, a plurality of measurement designated regions which wereselected while the multiple selection button is being pressed arestored. As another method, by providing a “Select next region” menu onthe menu screen and designating this menu each time a measurementdesignated region is designated, the region of interest can bedesignated successively. In all of the foregoing methods, it ispreferable to prepare means for cancelling a part or all of thedesignations of the measurement designated region.

Moreover, in an embodiment of the present invention, after setting aplurality of measurement designated regions, it is possible to newlyselect the respective measurement designated regions using a pointingdevice and individually designate the scanning priority. In theforegoing case, the same scanning priority may be designated in aplurality of regions, or higher scanning priority may be set in theorder that the measurement designated region was set.

The foregoing processes are executed by the region designating unit 201and the system control unit 204, and correspond to theregion-of-interest setting unit and the priority setting unit in theacoustic wave measuring apparatus to which the present invention can beapplied.

First Embodiment

The operation of the photoacoustic measuring apparatus according to thefirst embodiment is now explained in detail with reference to thedrawings.

<Designation of Region of Interest>

A plurality of measurement designated regions, so called regions ofinterest, are designated by a user via the region designating unit 201.A specific example of the designation of the measurement designatedregion by the user is shown in FIG. 4. In the diagram, 406 represents aregion corresponding to the observed image, and is a planar range inwhich the acoustic probe can perform scanning. 401 to 405 aremeasurement designated regions that were designated by the user. 401 to403 are regions which are set with a high priority (let this be priority1), and 404, 405 are regions which are set with a low priority (let thisbe priority 2). As shown in the diagram, regardless of the setting ofpriority, it is also possible to designate the measurement designatedregions in a mutually overlapping state. The designated regions ofinterest are stored in the system control unit 204.

Moreover, in the foregoing case, the measuring conditions of thephotoacoustic measurement can also be set. In this embodiment, it isalso possible to set the number of acquisitions (cumulative number) ofthe photoacoustic data in the same coordinate position upon measuringthe measurement region. Here, let it be assumed that the cumulativenumber is set to 10 times.

When the user gives instructions for starting measurement, a measurementrequest message is sent from the system control unit 204 to theapparatus control unit 107. The processing contents of the measuringapparatus 100 in this embodiment are now explained with reference toFIG. 3, which is a processing flowchart of the controller unit 107.

<Calculation of Scanning Speed for Measurement>

When the apparatus control unit 107 receives a measurement requestmessage, the apparatus control unit 107 foremost calculates the scanningspeed for measurement and the number of scans required for obtaining thecumulative number desired by the user (S1). Let it be assumed that thenumber of elements of the acoustic probe in the main scanning directionis Enx elements, the element pitch is Ep (mm), the cumulative number ofphotoacoustic measurement is Mn, and the light-emitting frequency of thelaser light source is LHz (Hz). In order to simplify the explanation,when the cumulative number Mn is a multiple of the number of elementsEnx, the scanning speed Vx (mm/sec) of the acoustic probe and the laserlight source in the main scanning direction and the number of scans Snare calculated based on Formula (1) and Formula (2), respectively. Theprocessing of step S1 corresponds to the moving speed acquiring unit inthe acoustic wave measuring apparatus to which the present invention canbe applied.

Vx=Ep×LHz  (1)

Sn=Mn/Enx  (2)

In the case of this embodiment, since the number of elements of theacoustic probe 104 in the scanning direction is five elements,estimation can be performed 5 times when the acoustic probe 104 is to bemoved on the object surface, and 10 estimations can be performed if theacoustic probe makes one full round. Moreover, since the element pitchis 2 mm and the light-emitting frequency of the laser light source is 10Hz, the scanning speed upon measurement will be 20 mm/sec.

The foregoing calculation example of the scanning speed is an example ofa case using photoacoustic measurement. Upon applying an acoustic wavemeasuring apparatus of a type which transmits ultrasound waves to anobject and receives reflected waves thereof, the moving speed uponmeasurement can be similarly calculated based on the drive frequency ofthe acoustic probe and the element pitch of the acoustic probe in themain scanning direction.

The scanning speed and number of scans for measurement obtained asdescribed above are used for calculating the scanning region ordetermining the measurement order explained later.

<Calculation of Scanning Region>

Subsequently, the apparatus control unit 107 calculates the scanningregion as the region in which the acoustic probe actually performsscanning. Calculation of the scanning region is performed in thescanning priority order from the measurement designated region having ahigh scanning priority. Foremost, among the plurality of measurementdesignated regions that were designated, the inclusion region whichincludes all measurement designated regions of the scanning priority tobe focused is calculated (S2). In other words, a region which includesall of the measurement designated regions and which is the smallestrectangular region is obtained as the inclusion region. The scanningpriority is hereafter simply referred to as the “priority”.

FIG. 5 shows an image of the inclusion region of priority 1. Regions401, 402, 403 shown in FIG. 5 are the measurement designated regions ofpriority 1, and a rectangle 504 is the inclusion region that wascalculated from the measurement designated regions.

Subsequently, a scanning strip is assigned to the inside of theinclusion region of priority 1 (S3). A scanning stripe refers to arectangular region capable of moving the acoustic probe and the lightsource (hereinafter collectively referred to as the “measurementsystem”) in the main scanning direction. In this embodiment, the widthof the scanning stripe in the main scanning direction in the scanningplane of the acoustic probe becomes the length of scanning andmeasurement that were performed by the acoustic probe, and the width inthe sub scanning direction becomes the length of all element regions ofthe acoustic probe in the sub scanning direction. The scanning stripe ishereinafter simply referred to as the “stripe”.

In reality, while the region subject to photoacoustic measurement is athree-dimensional region including the depth direction, unlessseparately provided for herein, the two-dimensional projection plane onthe scanning surface of the measurement system is indicated as a“stripe”.

FIG. 6 shows an example of assigning the stripe. Stripes 601 a, 601 bare respectively stripes that were assigned to the inclusion region 504set with priority 1. In this embodiment, while the stripes are assignedto the inclusion region 504 in order from the top in a manner of liningthe stripes, any method may be used for assigning the stripes so as longas all measurement designated regions can be included in the stripe.

Subsequently, the stripe to be processed (hereinafter referred to as the“notable stripe”) is divided into an actual scanning region and anon-scanning region (S4). An actual scanning region is a region wherethe acoustic probe actually performs scanning for measuring themeasurement designated region, and a non-scanning region refers to theother regions. The actual scanning region is a region that includes themeasurement designated region among the regions included in the stripe.

FIG. 7 shows an example where the notable stripe has been divided. 701is a notable stripe, and 702, 703, 704 are regions that overlap with thenotable stripe 701 among the measurement designated regions 401, 402,403 having priority 1. 705 and 706 including the foregoing regions arethe actual scanning regions, and the intermediate region is thenon-scanning region.

Subsequently, the scanning region of the notable stripe is determined(S5). The scanning region determination is the processing of determiningwhether the divided regions in the stripe are classified as any one ofthe following three types.

(1) Region (continuous scanning region) subject to photoacousticmeasurement as a result of continuously moving (continuously scanning)the measurement system in the main scanning direction while acquiringthe acoustic waves.

(2) Region (moving region) in which the measurement system moves butphotoacoustic measurement is not performed.

(3) Region (fixed measuring region) that is measured (fixed measuring)by stopping the measurement system.

In step S5, whether the foregoing actual scanning region is to bemeasured via continuous scanning or measured via repeated fixedmeasuring is determined. Moreover, with respect to the non-scanningregion, whether to move the acoustic probe without performingmeasurement or perform continuous scanning is determined. Specifically,the scanning method of the respective regions or the moving method isdetermined so that the time required for the measurement of the notablestripe and movement processing becomes the shortest.

The processing time upon setting a region as the continuous scanningregion can be calculated by dividing the scanning distance by thecontinuous scanning speed Vx. Moreover, the processing time upon settinga region as the fixed measuring region can be calculated by dividing thelaser irradiation frequency by the cumulative number. Moreover, theprocessing time of the moving region can be calculated by dividing themovement distance by the simple moving speed of the drive apparatus. Theprocessing of step S2 corresponds to the region calculating unit in theacoustic wave measuring apparatus to which the present invention can beapplied, and the processing of steps S3 to S5 corresponds to thescanning method determining unit.

A specific calculation example of the scanning region determination isnow explained with reference to FIG. 7. 707 is the initial position ofthe acoustic probe.

With this calculation example, let it be assumed that the element pitchof the acoustic probe is 2 mm, the element region of the acoustic probeis a 10 mm square, the scanning speed during measurement is 20 mm/sec,the simple moving speed is 50 mm/sec, the light-emitting frequency ofthe light source is 10 Hz, and the cumulative number is 5 times. Let itbe further assumed that the length of the notable stripe 701 in the mainscanning direction is 50 mm, the actual scanning region 705 is 20 mm,and the actual scanning region 706 is 10 mm.

Note that, when performing continuous scanning, since measurement isperformed while moving the acoustic probe, there are cases where themovement distance of the acoustic probe becomes slightly longer than thelength of the actual scanning region (refer to FIG. 9). In thisembodiment, the scanning distance is calculated by adding a distance (10mm) for the amount of the element region of the acoustic probe.

Foremost, considered is a case where, after measuring the actualscanning region 705, the acoustic probe is moved short of the actualscanning region 706 by passing through the non-scanning region.

When the actual scanning region 705 is subject to continuous scanning,the distance required for scanning 705 will be 30 mm, and the simplemovement distance of the non-scanning region will be 10 mm. Thus, thescanning time will be 30/20=1.5 sec, the moving time will be 10/50=0.2sec, and the required time can be calculated as 1.7 sec.

Meanwhile, when the actual scanning region 705 is subject to fixedmeasuring, the simple movement of 10 mm will be performed a total of 4times, and the measurement requiring 0.5 sec will be performed twice.Thus, the measurement time will be 0.5×2=1 sec, the moving time will be40/50=0.8 sec, and the required time can be calculated as 1.8 sec. Thus,it can be seen that the measurement of the actual scanning region 705can be performed quicker via continuous scanning.

Next, considered is a case where, after measuring the actual scanningregion 706, the acoustic probe is moved outside the notable stripe.

When the actual scanning region 706 is subject to continuous scanning,the distance required for scanning 706 will be 20 mm, and the requiredtime can be calculated as 1 sec. Meanwhile, when the actual scanningregion 706 is subject to fixed measuring, the simple movement of 10 mmwill be performed a total of twice, and the measurement requiring 0.5sec will be performed once. Thus, the measurement time will be 0.5 sec,the moving time will be 20/50=0.4 sec, and the required time can becalculated as 0.9 sec. Thus, it can be seen that the measurement of theactual scanning region 706 can be performed quicker via fixed measuring.

In other words, it can be seen that the scanning can be performedquickest when the actual scanning region 705 is set as a continuousscanning region and the actual scanning region 706 is set as a fixedmeasuring region. The remaining portion will be the moving region. Notethat the foregoing explanation is of a case where scanning is performedonce, but the time required for measurement can be obtained with thesame logic even in cases where the number of scans is a plurality oftimes; for instance, performing scanning twice in a full round.

The foregoing process of calculating the scanning region (steps S4 andS5) is repeated for all stripes, and the scanning region calculation ofthe overall inclusion region is performed.

Moreover, the processing of foregoing steps S2 to S5 is furtherperformed in priority order, and the same scanning region is calculatedfor each set priority.

<Determination of Scanning Track>

Subsequently, the apparatus control unit 107 determines the scanningorder among the actual scanning regions regarding the respectivescanning regions that were calculated for each priority (S6). Thedetermination criteria is to determine an order which will shorten thetotal measurement time of the measurement regions of all priorities, andshorten the displacement of the measurement system. The processing ofstep S6 corresponds to the scanning path identifying unit in theacoustic wave measuring apparatus to which the present invention can beapplied.

The processing of step S6 is explained in further detail in theflowchart of FIG. 8. When step S6 is started, processing of the stripewith the highest priority is started. Foremost, the actual scanningregion to be scanned is determined (S11). In the initial processing, theactual scanning region to be scanned is the actual scanning region thatis closest to the acoustic probe.

Subsequently, information of the actual scanning region is added to themeasuring track list (S12). The measuring track list records, at least,the measurement start coordinates, measurement method (continuousscanning measuring or fixed measuring), and information regarding thescanning distance. Note that, when there are a plurality of actualscanning regions in the same stripe, all actual scanning regions areadded to the measuring track list.

When there are unprocessed regions of the same priority, the sameprocessing is performed with the actual scanning region of the closestdistance to the measurement end coordinates of the added actual scanningregion as the subsequent destination.

When the processing of all stripes of the same priority is complete, thesame processing is performed regarding one lower priority. As a resultof performing the foregoing processing, information of the actualscanning region to be scanned will be listed in the scanning executionorder, and stored for each priority.

The apparatus control unit 107 refers to the measuring track list thatwas stored according to the foregoing procedure, and executesmeasurement while moving between the actual scanning regions (S7). Theprocessing of step S7 corresponds to the scanning unit in the acousticwave measuring apparatus to which the present invention can be applied.

The photoacoustic measuring apparatus according to this embodimentcalculates the region to be scanned by the measurement system in thepriority order based on the measurement designated region and prioritydesignated by the user, and determines the track on which themeasurement system is to move upon performing the photoacousticmeasurement. Consequently, the user is no longer required to set thescanning track, and can concentrate on the designation of the region ofinterest.

Moreover, the photoacoustic measuring apparatus according to thisembodiment comprises moving speed acquiring unit for calculating thecontinuous scanning speed, region calculating unit for determining thetime required for the measurement and determining the scanning region,and scanning path identifying unit which uses the movement distanceother than measurement as the measuring condition. Consequently, incomparison to a case of performing simple scanning scheduling such assubjecting all regions to continuous scanning, it is possible toefficiently calculate the scannable track, and thereby shorten themeasurement time.

Note that the moving speed acquiring unit (step S1) may be omitted ifthe moving speed and cumulative number are defined there is no need tocalculate the same. Moreover, a part of the scanning method determiningunit (steps S4 and S5) may also be omitted if there is no need toperform scanning region determination in the same priority. Even withthe foregoing configurations, it is possible to scan the plurality ofregions of interest in the priority order designated by the user, andadditionally yield an effect of being able to shorten the measurementtime.

Note that the receiving elements of the acoustic probe are not limitedto the grid pattern of this embodiment, and may also be a honeycombshape, a hound's-tooth shape, or other arrangement. The determination ofthe moving speed of the probe is not limited to the method illustratedin this embodiment, and various algorithms may be applied for adjustingthe scanning speed in dependence of the measuring conditions orapparatus configuration. Moreover, the scanning speed calculationfunction in this embodiment aims to obtain the probe moving speed formeasurement and, therefore, the reference parameters and algorithms arenot limited to those described in this embodiment.

Second Embodiment

The second embodiment is the mode of detecting a portion which overlapswith the regions of different priorities and optimizing the shape of theregions in step (S4) of dividing the scanning region shown in the firstembodiment. The processing other than step S4 and the systemconfiguration are the same as the first embodiment.

FIG. 9 is a diagram showing the state of data accumulation of the regionthat was captured while moving the acoustic probe. In the diagram, theobserver's right-side direction is the main scanning direction. Thecheckered rectangle represents the location where the receiving elementsof the acoustic probe existed upon performing photoacoustic measurementwhile shifting the acoustic probe in the main scanning direction oneelement at a time. In order to perform photoacoustic measurement whileshifting the acoustic probe in the main scanning direction one elementat a time, the scanning region will be, as shown in the diagram, filledby grids of the element size of the acoustic probe without any spacetherebetween. Note that, in this embodiment, let it be assumed that thecumulative number has been set to 5 times.

The numbers in the grid show number of times that photoacousticmeasurement was performed; that is, the cumulative number ofphotoacoustic measurement, at that location. A region 801 is the actualscanning region, and a region where estimation is performed 5 times.Since scanning and estimation are performed while shifting the acousticprobe in the main scanning direction one element at a time, this meansthat there will constantly be four elements' worth of excess data beforeand after the actual scanning region to be measured.

FIG. 10 shows an example of a case where a region of high priority(first priority) and a region of low priority (second priority) overlapwith each other. As shown in FIG. 10A, let it be assumed that anunmeasured region 901 of low priority is set so as to overlap with themeasured region 801 of high priority. In the foregoing case, asdescribed above, there will be data in which the cumulative number isless than 5 obtained during the measurement of the region 801.

In other words, when actual scanning regions of different prioritiesoverlap respectively, the actual scanning region can be reduced byreusing the data obtained upon scanning the region of high priority forthe region of low priority. Specifically, in addition to the regions inwhich estimation has been performed 5 times, the region may be furtherreduced in an amount of four elements so as to achieve a region 902shown in FIG. 10B. When continuous scanning is performed to the region902, since four elements' worth of data on the right side can besimilarly acquired, it is possible to obtain a cumulative number of 5times for all regions. In other words, it is possible to shorten themeasurement time since there is no need to move the distance of thereduced amount of eight elements.

In order to realize the foregoing function, in this embodiment, thephotoacoustic wave measuring apparatus according to the first embodimentis additionally equipped with a storage region in which the actualscanning region is further divided based on the element pitch of theacoustic probe, and the cumulative number of each of the divided regionsis mapped.

In addition, upon performing the processing of step S4, the scheduledcumulative number associated with the measurement is mapped to each ofthe divided regions. Upon performing the scheduling of low priority, theportion in which the predetermined number of estimations is completeregarding the determination of the measurement region is excluded fromthe actual scanning region. Moreover, even when it is less than thepredetermined number of times, any region that is overlapping with thepreviously measured region is determined to be a portion capable ofreusing the measured data, and also excluded from the actual scanningregion. In other words, the actual scanning region is reduced so as toinclude only the unmeasured regions.

In normal measurement processing, any region that does not satisfy thecumulative number set in the measuring conditions such as the regionoutside the region 801; that is, excess data, is erased. Nevertheless,in this embodiment, since all cumulative data is stored for eachcoordinate until all measurement is complete, it is possible to divertthe data upon measuring the actual scanning region of low priority, andthereby improve the measuring efficiency.

Note that, in this embodiment, while a region that has been estimatedeven once was excluded from the actual scanning region, thedetermination of exclusion is not limited to the case that wasillustrated in this embodiment. For example, the reference cumulativenumber or the like may also be changed according to the cumulativenumber of data, probe shape, sensitivity distribution, or the like.

Moreover, while this embodiment determined the overlap of regions instep S4 of dividing the scanning region, this may also be performed inother steps so as long as the processing can exclude the overlap ofregions of different priorities. For example, it is also possible todetermine the overlap of regions in step S2 of determining the inclusionregion per priority.

Third Embodiment

The third embodiment is a mode of changing the assignment method in step(S3) of assigning the stripes to the inclusion region. Upon assigningthe stripes to the inclusion region, the stripe arrangement position isadjusted so that measurement of regions of all priorities is completedwith the shortest possible scanning distance. Note that the processingother than step S3 and the system configuration are the same as thesecond embodiment.

With the photoacoustic measuring apparatus according to the first andsecond embodiments, since the photoacoustic measurement is performed instripe units, excess regions will be measured when they are smaller thanthe height of the actual scanning regions in which the measurementdesignated regions designated by the user. If it is possible to measurethe measurement designated region, the excess regions may be locatedanywhere, and the stripes may be moved in the sub scanning direction inthe amount of the width of the excess region.

FIG. 11 is an explanatory diagram of a case where an excess datameasurement region occurs. In FIG. 11A, regions 1001 and 1002 are theactual scanning regions designated as being high priority (priority 1),a region 1003 is the actual scanning region designated as being lowpriority (priority 2). The stripes 1004 and 1005 are stripes that wereassigned for measuring the actual scanning regions designated as beingpriority 1. In the first and second embodiments, the stripe arrangementwill be of the illustrated shape since the stripes are assigned, inorder from the top, to the inclusion region of each priority.

When the region 1003 of low priority is to be measured after measuringthe regions 1001, 1002, the unmeasured region will be shown as anangular C-shape as shown in FIG. 11B. In other words, in order tomeasure the entire region 1003 of low priority, it is necessary to newlymeasure regions 1007 to 1009. Assuming that the horizontal width of theregions 1007, 1009 is 25 mm and the horizontal width of the region 1008is 10 mm, the distance that needs to be newly measured will be25+10+25=60 mm.

Meanwhile, upon measuring the regions 1001, 1002, it is possible toarrange the stripes in displacement as shown in FIG. 11C. In theforegoing case, the unmeasured region of the region 1003 will bedisplayed as an L-shape as shown in FIG. 11D. In other words, in orderto measure the entire region 1003, it is necessary to newly measureregions 1010 to 1012. Based on the same calculation as the case of FIG.11B, the distance that needs to be newly measured will be 10+10+25=45 mmand, therefore, in comparison to the case of making no adjustment, thescanning distance upon measuring the regions of low priority can beshortened by 15 mm. Note that, upon performing continuous scanning,while the length of the region to be measured and the scanning distanceof the acoustic probe will slightly differ, these are considered to bethe same in the present invention.

Step S3 in this embodiment disposes stripes in the inclusion region of apredetermined priority, and thereafter determines whether there is aregion which overlaps with a region of one lower priority. Here, ifthere is an overlapping region, the arranged stripes are shifted in thesub scanning direction, and a position which will shorten the scanningdistance upon measuring the regions of low priority is detected.

An example of shifting the stripes is now explained. In thisexplanation, the main scanning direction is the x axis and the subscanning direction is the y axis.

In FIG. 11A, d1 is the distance of the excess portion of the measurementregion of the region 1001 of priority 1 in the sub scanning direction.Since the region 1001 requires a height that is worth two stripes forthe scanning, when the number of elements of the probe in the subscanning direction is Eny and the element pitch is Ep, the requiredheight of the scanning stripe can be calculated as 2×Eny×Ep.

Here, when the y coordinates of the uppermost part of the region ofpriority 1 is Uy1, and the y coordinates of the lowermost part of theregion of priority 1 is Ly1, the excess range d1 of the region 1001 inthe sub scanning direction will be (2×Eny×Ep−Uy1−Ly1). Note that, in thecase of FIG. 11, Uy1 will be the y coordinates of the uppermost part ofthe region 1001, and Ly1 will be they coordinates of the lowermost partof the region 1001.

In FIG. 11A, d2 is the difference between the uppermost part of theregion of priority 2 and the uppermost part of the region of priority 1.Here, when the y coordinates of the uppermost part of the region ofpriority 2 is Uy2, d2 can be represented as Uy2−Uy1. Thus, if d1>0 andd2>0, there will be a margin for adjusting the stripe position at theupper part in the sub scanning direction.

Subsequently, whether d1 and d2 correspond to any one of the followingthree conditions is determined.

<Condition 1>

When d2 is a distance that is not smaller than the integral multiple (Ntimes) of Eny×Ep; that is, when d2≧N×Eny×Ep is satisfied, N-number ofstripes are disposed at the upper part of the measurement region of theregion 1003 of priority 2. Here, when (d2−N×Eny×Ep)≦d1, the stripes formeasuring the regions of priority 1 are shifted upward by (d2−N×Eny×Ep).

<Condition 2>

When d1≧d2, the stripes for measuring the regions of priority 1 areshifted to a position shifted upward by d2; that is, shifted to theupper end of the region 1003 of priority 2.

<Condition 3>

When d2<Eny×Ep, the upper limit position of the stripes for measuringthe regions of priority 1 is shifted to the same position as the upperlimit position of the regions of priority 1. The upper end of thestripes for measuring the regions of priority 2 is started from the sameposition as the upper limit of the regions of priority 2, and themeasurement region thereof will overlap with the regions of priority 1.

Based on the foregoing method, candidates of the displacement positionof the stripes for measuring the regions of priority 1 are determined.When the candidates of the displacement position are determined, thescanning distance upon measuring the regions of low priority iscalculated, and, upon determining whether the scanning distance becomesshorter before and after shifting the stripes, the ultimate stripeposition is determined.

Note that, when the scanning distance for measuring the regions of lowpriority will be the same regardless of how the stripes are shifted, thestripe position will remain unchanged.

As a result of performing the foregoing processing in addition to theprocessing of step S3 in the second embodiment, it is possible to reducethe scanning distance to the regions of low priority, and reduce thetime required for performing measurement.

Note that, while this embodiment described an example of processing theactual scanning region of the highest priority, this embodiment may beapplied to any priority so as long as there is one lower priority.Moreover, in this embodiment, when the overlapping with regions of onelower priority is determined and the stripe position is adjusted, butthere are still three or more priorities, it is also possible to furtherdetermine the overlapping with regions of even lower priority.

Moreover, the method of shifting the stripe is not limited to theexample illustrated in this embodiment. For example, there are caseswhere the measurement accuracy is improved and the scanning time isshortened based on scheduling in which the stripes are overlapped in thesub scanning direction according to the data accumulation, shape ofprobe, sensitivity distribution, and the like. Moreover, while thisembodiment adopted a mode of moving the arrangement position afterassigning the stripes, it is also possible to calculate the optimalposition before assigning the stripes so as to directly assign thestripes.

Moreover, it is also possible to define the amount of displacement ofthe stripes in advance, and perform calculations of all patterns. Forexample, when the stripe adjustment margin is 5 mm, it is possible toperform 5 calculations by shifting the stripes 1 mm at a time, andadopting the stripe in which the scanning distance becomes shortest.Moreover, while this embodiment adjusted the position of the stripes soas to shorten the scanning distance upon measuring the regions of lowpriority, the scanning time may also be used as the determinationcriteria in substitute for the scanning distance.

The foregoing embodiments are merely an example, and the presentinvention may be implemented by being changed as needed to the extentthat such change does not deviate from the gist of this invention.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

1. An acoustic wave measuring apparatus, comprising: a probe configuredto measure an acoustic wave propagated from an object; a moving unitconfigured to move the probe with respect to the object; a regiondesignating unit configured to designate a plurality of measurementregions for receiving the acoustic wave on the object; and a controllingunit configured to determine a path including the plurality ofmeasurement regions on which the probe is moved by the moving unit andoperation of the probe on the path, wherein the operation of the probeis determined based on information relating to positions of theplurality of measurement regions, and wherein the path is determinedbased on the information relating to positions of the plurality ofmeasurement regions and the operation of the probe.